On Wed, 8 Feb 2006 10:40:36 -0500, you wrote:

>I'm about to migrate a project from a 452 to the 4520.  While comparing the
>datasheets I noticed that RA4 on the 452 is shown as being "open drain when
>configured as output", but on the 4520 it is never mentioned that RA4 is
>also open drain.  In my board design I have the anode of an LED connected to
>RA4 with the cathode connected to +5V via a 1K resistor, 
>so I will have to
>reverse it and change my code, very easy to do but I was under the
>impression that the 4520 was pin-compatible with the 452.  Is this not the
>case?
>
>Regards,
>Bob

Yes - on the 4520 it pulls up as well as down, but the polarity is the same. 
This should not affect anything unless you are relying on it being open-drain.  
If you have it connected as you stated above (cathode to +5) it won't light on either chip, unless
something else is pulling the pin to > 5V, which is not a good idea...


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